Fuel oil compositions with improved pour point characteristics

ABSTRACT

POUR POINT CHARACTERISTICS OF MIDDLE DISTILLATE FUEL OILS ARE IMPROVED BY INCORPORATING IN SUCH FUEL OILS ABOUT 0.0001-5% BY WEIGHT OF AN OIL-SOLUBLE TERPOLYMER OF A MONOMERIC C2 TO C9 ALKYL ESTER OF THIOLACRYLIC ACID, A MONOMERIC C10 TO C20 ALKYL ESTER OF THIOLACRYLIC ACID AND A MONOMERIC BRANCHED-CHAIN C3 TO C8 ALKYLAMINOETHYL ESTER OF METHACRYLIC ACID, SAID TERPOLYMER HAVING AN AVERAGE MOLECULAR WEIGHT OF AT LEAST ABOUT 2,000. THE TERPOLYMER CONTAINS ABOUT 5 TO ABOUT 45 PERCENT BY WEIGHT OF THE C2 TO C9 ALKYL ESTER OF THIOLACRYLIC ACID, ABOUT 45 TO ABOUT 85 PERCENT BY WEIGHT OF THE C10 TO C20 ALKYL ESTER OF THIOLACRYLIC ACID AND ABOUT 5 TO ABOUT 15 PERCENT BY WEIGHT OF THE BRANCHED-CHAIN C3 TO C8 ALKYLAMINOETHYL ESTER OF METHACRYLIC ACID.

United States Patent Ofice 3,598,551 Patented Aug. 10, 1971 3,598,551 FUEL OIL COMPOSITIONS WITH IMPROVED POUR POINT CHARACTERISTICS Arvid Ek, Shaler Township, Allegheny County, Edward Mitchell, Valencia, and Frederick E. Scypinski, Monroeville, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa. No Drawing. Filed Mar. 12, 1970, Ser. No. 19,099 Int. Cl. C101 1/18, 1/24 US. CI. 44-62 4 Claims ABSTRACT OF THE DISCLOSURE Pour point characteristics of middle distillate fuel oils are improved by incorporating in such fuel oils about 0.001-5% by weight of an oil-soluble terpolymer of a monomeric C to C alkyl ester of thiolacrylic acid, a monomeric C to C alkyl ester of thiolacrylic acid and a monomeric branched-chain C to C alkylaminoethyl ester of methacrylic acid, said terpolymer having an average molecular weight of at least about 2,000. The terpolymer contains about 5 to about 45 percent by weight of the C to C alkyl ester of thiolacrylic acid, about 45 to about 85 percent by weight of the C to C alkyl ester of thiolacrylic acid and about 5 to about percent by weight of the branched-chain C to C alkylaminoethyl ester of methacrylic acid.

This invention relates to fuel oil compositions and more particularly to middle distillate fuel oil compositions having improved pour points.

The pour points of an oil is defined as the lowest temperature at which the oil will pour or flow when chilled without disturbances under specified conditions. Problems associated with the pour point of an oil result from the formation of solid or semi-solid waxy particles in the oil when the oil is subjected to a temperature equal to or lower than its pour point. When solid or semi-solid waxy particles are formed in an oil, its distribution and filtration is rendered difficult or impossible. Pour point problems associated with the storage and use of heavy oils such as lubricating oils has long been recognized. While similar problems associated with the pour point of middle distillate fuel oils have also existed, the prior rather limited use of such oils has not given rise to great concern in this respect. More recently, with increased use of middle distillate fuel oils at temperatures approximating their pour points, the problems and difliculties encountered in their use have become more acute. In the transportation, distribution and storage of furnace oils or diesel oils, temperatures in the order of l5 F. and lower may be encountered. Jet fuels may encounter much lower temperatures, for example, 40 to 50 F. because of the altitudes at which jet aircraft are capable of operating. At such low temperatures, crystallization and solidification of wax in the oil often occurs. When solidification of the wax is encountered, the flow of oil is decreased and in some instances, completely stopped which results in equipment failure.

In the past, the low temperature flow characteristics of a lubricating oil have been improved by incorporating in the oil a compound which is effective in lowering the pour point of the lubricating oil. Unfortunately, compounds which are normally effective in lubricating and other heavy oils are generally ineffective in a distillate fuel oil. The ineffectiveness of such compounds may be due at least in part to differences in the structure and composition of the waxes which occur in lubricating oils and of the waxes present in middle distillate fuel oils. The term middle distillate fuel oils as used herein is intended to refer to distillate petroleum fractions boiling within the range of about 300 to about 750 F. and include furnace oil, diesel oil, kerosene and aviation jet fuel.

The difficulty encountered in the low temperature flow characteristics of middle distillates has been overcome in some instances by using lighter fractions as fuel oils, i.e., by lowering the maximum distillation temperature at which the distillate fraction is collected. However, a lowering of the maximum distillation temperature results in a loss of valuable distillate product. It has also been suggested that the pour point of distillate fuel oil fractions may be improved by urea dewaxing. Separately or in combination lowering the end points of distillate fuel oils and dewaxing are economically unattractive.

It is among the objects achieved by the present invention to provide a compound which effectively reduces the pour point characteristics of middle distillate fuel oils and to provide compounded middle distillate fuel oils having pour points which are lower than the uncompounded fuel oils.

In accordance with the present invention, we have found that the pour point characteristics of a middle distillate fuel oil can be improved by incorporating in the fuel oil a small amount of an oil-soluble terpolymer of (a) a monomeric alkyl ester of thioacrylic acid whose alkyl ester substituent contains 2 to 9 carbon atoms, (b) a monomeric alkyl ester of thiolacrylic acid whose alkyl ester substituent contains 10 to 20 carbon atoms and (c) a monomeric branched-chain alkylaminoethyl ester of methacrylic acid whose alkyl substituent contains 3 to 8 carbon atoms. The average molecular weight of the terpolymer is normally greater than about 2,000 and preferably greater than about 5,000 as determined by conventional methods. Usually the average molecular weight of the terpolymer will be in the range of about 50,000 to about 500,000 but the molecular weight can be as much as 2,000,000 or more, provided, the molecular weight is not so large as to render the terpolymer insoluble in the fuel oil to which it is added. The terpolymer is formed by copolymerizing the monomeric C to C alkyl ester of thiolacrylic acid, the monomeric C to C alkyl ester of thiolacrylic acid and the monomeric branched-chain C to C alkylaminoethyl ester of methacrylic acid in amounts such that the C to C alkyl thiolacrylate comprises about 5 to about 45 percent by weight of the terpolymer, the C to C alkyl thiolacrylate comprises about 45 to about percent by weight of the terpolymer and the branchedchain C to C alkylaminoethyl methacrylate comprises about 5 to about 15 percent by weight of the terpolymer.

The monomeric C to C alkyl esters of thiolacrylic acid suitable for use in preparing the oil-soluble terpolymers for the purposes of this invention are illustrated by the ethyl, propyl, isopropyl, butyl, isobutyl, tertiary butyl, amyl, isoamyl, heXyl, sec-hexyl, octyl isooctyl and nonyl esters of thiolacrylic acid.

The monomeric C to C alkyl esters of thiolacrylic acid suitable for use in preparing the oil-soluble terpolymers for the purposes of this invention are illustrated by the decyl, dodecyl, tridecyl, tetradecyl, sec-tetradecyl, hexadecyl, octadecyl, isooctadecyl and eicosyl esters of thiolacrylic acid.

The monomeric branched-chain alkylaminoethyl methacrylates suitable for use in preparing the oil-soluble terpolymers for the purposes of the invention are the branched-chain alkylaminoethyl esters of methacrylic acid whose alkyl substituent contains from 3 to 8 carbon atoms. Illustrative of such branched-chain alkyl substituents are isopropyl, sec-butyl, isobutyl, tertiary butyl, isoamyl, isohexyl, isooctyl and tertiary octyl groups.

Specific examples of terpolymers which can be used according to the invention are the 118:1 weight ratio, respectively, terpolymers of ethyl thiolacrylate:n-decyl thiolacrylate :isopropylaminoethyl methacrylate n-propyl thiolacrylate n-decyl thiolacrylate t-butylaminoethyl methacrylate n-butyl thiolacrylate n-dodecyl thiolacrylate t-butylaminoethyl methacrylate n-butyl thiolacrylate :n-tetradecyl thiolacrylate t-butylaminoethyl methacrylate t-butyl thiolacrylate n-tetradecyl thiolacrylate t-butylaminoethyl methacrylate n-butyl thiolacrylate:n-hexadecyl thiolacrylate:isoamylaminoethyl methacrylate n-butyl thiolacrylate:n-octadecyl thiolacrylatezisohexylaminoethyl methacrylate n-hexyl thiolacylatezn-eicosyl thiolacrylate Z-ethylhexylaminoethyl methacrylate n-hexyl thio acrylate sec-tetradecyl thiolacrylate t-butylaminoethyl methacrylate sec-hexyl thiolacrylate :sec-tetradecyl thiolacrylate secbutylaminoethyl methacrylate n-octyl thiolacrylate :n-dodecyl thiolacrylate t-butylaminoethyl methacrylate n-nonyl thiolacrylate n-dodecyl thiolacrylate t-butylaeminoethyl methacrylate Other oil-soluble terpolymers of the class disclosed herein can also be used so long as the weight percent of the monomeric C to C alkyl ester of thiolacrylic acid is within the range of about 5 to about 45 percent by weight of the terpolymer, the weight percent of the monomeric C to C alkyl ester of thiolacrylic acid is within the range of about 45 to about 85 percent by weight of the terpolymer and the weight percent of the monomeric branched-chain C to C alkylaminoethyl ester of methacrylic acid is Within the range of about 5 to about percent by weight of the terpolymer. Examples of such other terpolymers whose use is included by the invention are terpolymers whose weight ratio of monomers (a) C to C alkyl thiolacrylate, (b) C to C alkyl thiolacrylate and (c) branched-chain C to C alkylaminoethyl methacrylate, respectively are 1:8.5:0.5; 0.5 18:1.5; 1:7.5:1:5; 217:1; 3:621; 425:1; 4.5:4.5:l; and 4.5:5:0.5. Particularly good results have been obtained with the terpolymer of n-butyl thiolacrylate:n-tetradecyl thiolacrylate: t-butylaminoethyl methacrylate in a weight ratio of 4:5: 1, respectively.

The amount of the terpolymer added to the distillate fuel oil composition in accordance with the present invention is that amount which is sufiicient to improve the pour point of the distillate. The minimum and optimum effective proportions can vary somewhat according to the nature of the particular terpolymer. In general, the terpolymer is included in a petroleum middle distillate in an amount of about 0.001 to about 5 percent by weight of the petroleum distillate, preferably about 0.01 to about 0.5 percent by weight of the distillate. Good results have been obtained with the 4:5:1 terpolymer of n-butyl thiolacrylatezn tetradecyl thiolacrylatezt butylaminoethyl methyl methacrylate in amounts of about 0.02 to about 0.1 percent by weight.

The terpolymer pour point depressants described herein can be incorporated in a wide variety of petroleum distillates, such as for example, diesel fuels, jet fuels, furnace oils, heater oil fractions, kerosene, gas oils, and other light oils. The fuel oil may be of virgin of cracked petroleum stock, or mixtures thereof, boiling in the range of about 300 to about 750 F., and preferably in the range of about 350 to about 650 F. The fuel oil may contain cracked components, such as, for example, those derived from cycle oils or cycle oil cuts boiling above gasoline, usually in the range of about 450 to about 750 F. and may be derived by catalytic or thermal cracking. Highsulfur containing and low-sulfur containing oils such as diesel oils may be used.

Preferred distillate fuel oils which are improved in accordance with the invention have an initial boiling point within the range of about 350 to about 475 F., and an end point in the range of about 500 to about 650 F., an API gravity of at least about 30 and a flash point (P-M) not lower than about 110 F.

The herein described terpolymers can be incorporated in the fuel oil in any convenient way. Thus, the terpolymer can be added directly to the fuel oil by dissolving the terpolymer in the fuel oil at the desired level of concentration. Alternatively, the terpolymer may be blended with suitable solvents to form concentrates that can be readily dissolved in the appropriate fuel oils at the desired concentrations. The concentrate should contain at least 10 percent by weight of the terpolymer pour point depressant and preferably about 25 to about percent by weight of the terpolymer. The solvent in such a concentrate may be present in amounts of about 35 to about percent by weight. The solvent preferably boils within the range of about to about 700 F. Suitable solvents which can be used for this purpose are naphtha, kerosene, benzene, xylene, toluene, hexane, light mineral oil and mixtures thereof. The particular solvent selected should, of course, be selected so as not to adversely affect the other desired properties of the ultimate fuel oil composition. Thus, the solvent should preferably burn without leaving a residue and should be non-corrosive with respect to metal, specifically ferrous metals.

If desired, the terpolymer pour point depressants described herein can be employed in conjunction with other additives commonly used in petroleum products. Typical of such additives are rust and corrosion inhibitors, antiemulsifying agents, anti-oxidants, dispersants, dyes, haze inhibitors, anti-static agents and the like. In some instances, it may be desirable to prepare additive concentrates which can be used to add several desired additives simultaneously. Dissolution of the terpolymer or additive concentrate may be facilitated by mixing accompanied with mild heating.

The oil-soluble terpolymers disclosed herein can be prepared in any convenient Way. For example, they can be prepared by causing the desired monomers to react in the weight ratios disclosed in the presence of a diluent, preferably a solvent such as toluene, benzene, ethyl acetate, mineral oil or other solvent having similar chain transfer activity, at a temperature in the range of 0 C. to 150 C., preferably 25 to C., in the presence of a few hundredths percent to two percent, preferably 0.02 to 1.0 percent, of a free radical catalyst such as tertiary butyl hydroperoxide, benzoyl peroxide, lauroyl peroxide or alpha, alpha-azodiisobutyronitrile, preferably in the substantial absence of oxygen for about 30 minutes to about 35 hours, or until the rate of formation of polymer molecules has declined substantially. The latter time is determined by periodic sampling of the reaction mixture and observing a decline in the rate of increase in the viscosity of the product. Alternatively,

' instead of the polymerization procedure described above,

with the invention can be prepared in any desired manner. Neither the monomers per se nor their method of preparation constitutes any portion of the invention. Tertiary octyl thiolacrylate, for example, can be prepared by the reaction of ft-chloropropionyl chlorideand tertiary octyl mercaptan to produce tertiary octyl-fi-chlorothiolpropionate according to the equation:

The tertiary octyl p-chlorothiolpropionate thus obtained is dehydrohalogenated at above 210 C. in the presence of N,N-dimethylaniline and a polymerization inhibitor such as hydroquinone to give tertiary octyl thiolacrylate according to the equation:

Tertiary butylaminoethyl methacrylate can be prepared by e sterification of methacrylic acid with tertiary butylaminoethanol. Tertiary butylaminoethanol, in turn, can be prepared by treating tertiary butylamine with ethylene oxide.

The invention will be more fully understood from a consideration of the following specific example illustrating the preparation of a particularly effective terpolymer of n-butyl thiolacrylate:n-tetradecyl thioacrylatezt-butylaminoethyl methacrylate (4:5: 1).

EXAMPLE A concentrate comprising a 60 percent by weight solution in a light mineral oil of a 4:5:1 weight ratio terpolymer of n-butyl thiolacrylate:n-tetradecyl thiolacrylatezt-butylaminoethyl methacrylate is prepared by heating 2.4 grams of n-butyl thiolacrylate, 3.0 grams of ntetradecyl thiolacrylate, 0.6 gram of t-butylaminoethyl methacrylate and 36.0 milligrams (0.6% by weight) of alpha, alpha-azodiisobutyronitrile in 4. grams of a light mineral oil as a reaction solvent, at about 50 C. for about 24 hours, with nitrogen bubbling through the reaction mixture during the reaction. The product thus obtained comprises a 60 percent by weight oil solution of the terpolymer of n-butyl thiolacrylate:n-tetradecyl thiolacrylate:t-butylaminoethyl methacrylate (4:521). The average molecular weight of the terpolymer thus obtained is about 2.5 10

The foregoing example is illustrative only. Similar terpolymers can be obtained by copolymerizing other monomeric alkyl esters of thiolacrylic acid with other monomeric branched-chain alkylaminoethyl esters of methacrylic acid as well as in other monomer proportions disclosed herein. For example, there can be prepared in accordance with the method indicated above, the terpolymers of (a) monomeric ethyl, propyl, isopropyl, nbutyl, isobutyl, tertiary butyl, n-arnyl, isoamyl, n-octyl, Oxo octyl, 2-ethylhexyl and n-nonyl thiolacrylates, (b) monomeric n-decyl, n-dodecyl, 0x0 tridecyl, n-tetradecyl, sec-tetradecyl, n-hexadecyl, n-octadecyl, isooctadecyl and eicosyl thiolacrylates and (c) monomeric isopropyl, secbutyl, isobutyl, tertiary butyl, isoamyl, isohexyl, isooctyl and tertiary octyl aminoethyl methacrylates, wherein the weight ratio of (a):(b):(c), respectively, is 1:821; 1:85:05; 0.5:8:l.5; 1:7.5:1.5; 2:7:1; 3:6:1; 4:5:1; 4.5 :4.5:1 and 4.5:5:0.5. Terpolymers having other ratios are similarly prepared by copolymerizing 5 to 45 parts by weight of the C to C alkyl thiolacrylate, 45 to 85 parts by weight of the C to C alkyl thiolacrylate and 5 to parts by weight of the C to C alkylaminoethyl methacrylate.

In order to illustrate the improved pour point characteristics of a middle distillate fuel oil when compounded in 'accordance with the invention, pour points (ASTM D97-66) were obtained on the fuel oil with and without the addition of the terpolymer of n-butyl thiolacrylate:ntetradecyl thiolacrylatezt butylaminoethyl methacrylate (4:511). A comparative evaluation was made with a terpolymer not of the invention, i.e., terpolymer of n-butyl thiolacrylate:n-tetradecyl thiolacrylate:diethylaminoethyl methacrylate (4.5:1). The fuel oil used in illustrating the invention has the following typical characteristics.

When 0.04 percent by weight of the 60 weight percent oil solution of the terpolymer of n-butyl thiolacrylatezn-tetradecyl thiolacrylatezt butylaminoethyl methacrylate (4:5:1) of the example was added to the above middle distillate, the pour point of the resulting composition was --25 F. When 0.08 percent by weight of a 33 weight percent oil solution of the same 4:5 :1 terpolymer was added to the above middle distillate the pour point of the resulting composition was 30 F. When 0.08 percent by weight of a 50 percent oil solution of the same 4:5:1 terpolymer was added to the above middle distillate, the pour point of the resulting composition was 30 In order to illustrate the lack of improvement obtained when the alkyl group of the alkylaminoethyl ester of methacrylic acid in the terpolymer is not a branchedchain alkyl group, the same fuel oil was evaluated with 0.04 percent by weight of the 60 weight percent oil solution of the terpolymer of n-butyl thiolacrylate:n-tetradecyl thiolacrylate:diethylaminoethyl methacrylate (4:521). The pour point of the resulting fuel oil composition was -10 F. The pour point of the fuel composition not of the invention was thus higher than the pour point of the fuel oil neat.

It is evident from the above that a terpolymer of nbutyl thiolacrylatezn-dodecyl thiolacrylate:t-butylaminoethyl methacrylate (4:5:1) has excellent pour depressing characteristics on a middle distillate fuel oil. It is further evident that when two ethyl groups are attached to the nitrogen atom of the aminoethyl ester of methacrylic acid, used in forming the terpolymer, the pour point of the middle distillate fuel oil is not improved.

While our invention has been described with reference to various specific examples and embodiments, it will be understood that the invention is not limited to such examples and embodiments and may be variously practiced within the scope of the claims hereinafter made.

We claim:

1. A distillate fuel oil composition comprising a major amount of a petroleum distillate boiling in the range of about 300 to about 750 F. and a small amount, sufficient to improve the pour point of said petroleum distillate, of an oil-soluble terpolymer of (a) a monomeric alkyl ester of thiolacrylic acid whose alkyl ester substituent contains 2 to 9 carbon atoms, (b) a monomeric alkyl ester of thiolacrylic acid whose alkyl ester substituent contains 10 to 20 carbon atoms, and (c) a monomeric branched-chain alkylaminoethyl ester of methacrylic acid whose alkyl substituent contains 3 to 8 carbon atoms, said terpolymer having an average molecular weight of at least about 2,000 and comprising about 5 to about 45 percent by weight of constituent monomer (a), about 45 to about percent by weight of constituent monomer (b) and about 5 to about 15 percent by weight of constituent monomer (c).

2. The fuel oil composition of claim 1 wherein said small amount is about 0.001 to about 5 percent by weight of the composition.

7 8 3. The fuel oil composition of claim 2 wherein con- References Cited stituent monomer (a) is n-butyl thiolacrylate, monomer v UNITED STATES PATENTS I (b) is n-tetradecyl thiolacrylate and monomer (c) 15 tbutylaminoethyl methacrylate. 2,4 3,267 7/1946 Davis 44-62X 4. A distillate fuel oil composition comprising a major 5 3,151,957 10/1964 Clough et 4462 amount of a petroleum distillate boiling in the range of 3,156,649 11/1964 Hewett et a1 4476X about 300 to about 750 F. and a small amount, sufficient to improve the pour point of said petroleum distil- DANIEL WYMAN Pnmary Exammer late, of an oil-soluble 4:5:1 weight ratio terpolymer of W, J, SHINE, A i tant Examiner n-butyl thiolacrylate:n-tetradecyl thiolacrylate:t-butylami- 10 U S C1 X R noethyl methacrylate having an average molecular weight of about 2.5 10 76 32 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,598,551 Dated August 10, 1971 Arvid Ek, Edward Mitchell and Frederick E. Scypinski It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 33, "points" should read --point--,

line 35, "disturbances" should read -disturbance--.

Column 5, line 12, "N,Ndimethylaniline" should read N,Ndiethylaniline.

Column 6, line 3, "(4.5:l)" should read --(4:5:l).

Signed and sealed this 28th day of December 1 971 (SEAL) Attest: I

EDWARD M.FLETCHER,JR. ROBERT 'GOTTSCHALK Attesting Officer Acting Commissioner of Patents 

